The present invention relates, in general, to patches for the hulls of ships, barges, and other vessels, and more particularly to an improved patch structure which consists of a plastic or rubber inflatable bladder covered on the interior side with a foam sealer layer and on the exterior surface with a woven wire net which reinforces the bladder and by which it is secured to the hull of the ship.
There is a serious and growing problem occurring in the navigable waters of this and other countries created by the increased consumption of chemical and petroleum products and the increasing use of tanker ships and barges for transporting such products. Such vessels are susceptible to damage not only from storms, but from collisions, grounding, and other accidents, with the result that oil and chemical spills are becoming commonplace at sea and in harbors and rivers. The public is becoming increasingly aware of, and sensitive to, the damage resulting from such spills, and there is a strong and growing demand that controls be provided to protect the environment and to reduce the high costs of cleaning up oil and other spilled materials and repairing the damage done.
One of the difficulties faced in trying to prevent the extensive damage caused by oil and other spills is the fact that once a hull is breached and it begins to leak, there has been no effective way to stop it, particularly when the cause of the breach is the grounding of a vessel. Although the prior art suggests numerous ways to seal a leaking hull, virtually all of such prior art patches were designed to prevent water from flowing into the hull; almost none were designed to prevent fluid from leaking out. Further, the rules applicable to many harbors and inland waters generally require that once a vessel begins to leak, it cannot be moved, but must be unloaded. Since such leaks often occur when a ship or barge has gone aground, it often occurs that the hull is virtually inaccessible, and unloading becomes a difficult, time consuming and costly exercise. Even if the vessel is accessible, unloading it does not stop the leak until the barge is virtually empty, and thus unloading does not prevent damage, but merely reduces its scope. Although this is a help, it does not solve the problem.
Because of the damage potential of a barge or ship full of oil, and because the cost of unloading such a hull if a leak occurs can be extremely high, and further because of the amount of insurance that must be carried to protect against such an event and against subsequent charges for damages caused by the leaking oil, the cost of transporting oil by ship or by barge has substantially increased in recent times. Accordingly, there is a strong demand for an effective, easy to use, and economical method and apparatus for patching leaking hulls, not only among environmentalists who are concerned with the irreversible damage done by leaking oil, but by shippers and owners in the industry who face severe economic pressures.
The prior art discloses numerous structures in the form of mats or the like which are designed to prevent leakage of water into a hull. Exemplary of this art are the following U.S. Patents :Nos. 136,817 to Cooper; 331,658 to Sooysmith; 353,718 to Tuck; 635,939 to Mason; 1,107,680 to Lucka; 1,306,938 to Achiha; 1,573,909 to Blumberg; 2,127,871 to Kozloff; and 2,446,190 to Oding. Each of the foregoing patents discloses some type of apparatus for closing holes which appear in hulls, and the bulk of them show the use of cables or lines passing around the hull for use in positioning the mat. U.S. Pat. No. 3,669,055 to Buce discloses a mat for sealing an opening in an oil tanker for preventing an inflow of water and an outflow of oil. This patent also uses cables or lines passing at least part way around the hull for locating the patch in the desired area.
Although each of the foregoing patents discloses a patch arrangement, it has been found that these structures in fact are ineffective, and do not solve the problem which exists in attempting to retain a full load of oil in a hull such as that of a supertanker or a river barge. Although the patent to Buce suggests that such patches may be used for retention of oil, the approach taken by that patent is essentially the same as that taken by the earlier patents; namely, the provision of a series of cables or lines extending around the hull and pressing against the outside of the patch to hold it in position. Because of the moment arms involved, a cable stretched in such a manner cannot be drawn tightly enough to secure a patch in sealing relationship to the outside surface of a hull. Further, most of the patches disclosed in thes patents are designed for use with relatively flat surfaces, and cannot be used in conjunction with irregular surfaces such as the curved portions of the hull on a ship, the relatively square corners on a barge, or the irregularity of the keel area. In addition, the prior art patches are unwieldy and difficult to handle and require special equipment which is not normally found on shipboard or with barges. Thus, they require a large investment in equipment, and do not help to reduce the overall costs of shipping such materials.